The IEEE 802.1aq standard (802.1aq), was published in 2012 and defines a routing solution for Ethernet that replaces prior routing solutions including Spanning Tree Protocols. 802.1aq is also known as Shortest Path Bridging or SPB. 802.1aq enables the creation of large numbers of logical Ethernet networks on native Ethernet infrastructures. 802.1aq employs a link state protocol (i.e., Intermediate System to Intermediate System (IS-IS)) to advertise network topology and logical network membership of the nodes in the network. The link state information is used to calculate shortest path trees from all bridges in the SPB region. The computations are done in an independent and distributed manner with each node generating its own forwarding tables to implement its part in SPB region-wide forwarding.
Data is encapsulated at the edge nodes of the networks implementing 802.1aq. This encapsulation can be in 802.1ah or tagged 802.1Q/p802.1ad frames. These frames are transported only to other members of the respective logical network. Unicast and multicast routing are also supported by 802.1aq. All such routing is done via symmetric shortest paths. Multiple equal cost shortest paths are supported. Implementation of 802.1aq in a network simplifies the creation and configuration of the various types of supported networks, including provider networks, enterprise networks and cloud computing networks. 802.1aq also increases bandwidth and reliability by improved use of the network mesh topology. By unblocking all paths, greater utilization can be obtained through the use of multiple equal cost paths. Improved convergence times and larger topologies can also be supported due to the simplification of synchronization of the view of the network across all nodes inherent to link state routing.
Virtual Private LAN Service (VPLS) is an approach to effecting Ethernet Virtual Private Networks (VPNs) over Multi-Protocol Label Switching (MPLS) networks. However, VPLS as currently specified does not provide for multiple unblocked attachment circuits for supporting SPB.
Prior VPLS implementations that support 802.1ah have typically only collocated the I-component with the PE and, as such, do not have a PBBN attached to any PE. Consequently, there is no means of supporting a backbone Ethernet networking component. Thus, in these prior systems there are no B-VIDs, and that function is null. There is no requirement for symmetric and congruent multicast trees, and VPLS itself is not necessarily congruent across an MPLS network. Therefore, in previous networks the unit of configured load spreading is the I-SID. VPLS supports “active-standby” multi-chassis uplinks (a.k.a., Multi-chassis Link Aggregation Group (MC-LAG)). Accordingly, there is a need to implement shortest path bridging support over a virtual private LAN service network to take advantage of SPB features with VPLS.